1. Field of the Invention
A method of configuring a diamond surface to a desired shape and polishing said diamond by use of a combination of diffusion smoothing, laser ablation controlled in real time by an interferometer and ion beam-assisted polishing.
2. Description of the Related Art
In the past, optical surfaces were ground and polished by artisans using techniques handed down through the generations. In more recent times, modern computer controlled cutting tools such as single point diamond turning machines and improved materials for cutting have been introduced such that the surface shapes of the optics could be approximated very closely by very fine controlled changes in the position of the cutting tool and then polishing the surface of the optics to smooth out ridges and roughness on the surface and thereby improve the optical scattering properties of the optic.
Beginning in the mid 1980s, various low-pressure Chemical Vapor Deposition (CVD) methods have been developed to produce diamond films and since then, the material quality has improved to the point that now CVD diamond can be used in demanding optical applications. Diamonds are highly transparent to light from the deep ultraviolet throughout the visible and infrared spectra. It is highly desirable to use diamond for optics and for other purposes due to its superior mechanical, thermal, and chemical properties, but diamond being the hardest material known, is difficult to shape and polish. Diamonds produced by current CVD methods are polycrystalline plates. The surface is rough and has to be shaped and polished to be useable in most applications. For high-quality optical components, the surface imperfections must be on the order of 1/100 of a wave length or less. Traditional means of producing lenses and other optic surfaces do not work with diamonds.
Many means have been proposed to smooth the surface of diamonds to make them useful in optics and other applications which require a smooth surface. These methods include polishing by conventional mechanical polishing with diamond dust, by reaction with oxygen or other gases, by laser ablation, by argon or other ion-beam irradiation, by hot metal lapping, and by electron discharge. However, some of these methods may result in inefficient diamond material removal, some of them may cause excessive and uneven etching and pitting and are either very expensive, extremely slow, or produce a rough surface having a low optical quality. Most importantly, none of the currently available diamond polishing methods assure an accurate surface figure.